Delay action pressure by-pass systems and valves therefor for hydraulic transmissions



May 10, 1960 1 HOCK ET AL 2,935,999

DELAY ACTION PRESSURE BY-PASS SYSTEMS AND VALVES THEREFOR FOR HYDRAULIC TRANSMISSIONS Filed Dec. 1, 1955 2 Sheets-Sheet x r Irl/111111171111111', A I

M qwslnn. C WHQMMM y 77 .Im/enfans May 10, 1960 J. HocK ET AL DELAY ACTION PRESSURE By-PAss SYSTEMS AND vALvEs THEREFDR FOR HYDRAULIC TRANsMssIoNs Filed Dec. 1, 1955 2 Sheets-Sheet 2 if 5y Pun 4 "Y mkv/5x55 DELAY ACTION PRESSURE BY-PASS SYSTEMS AND VALVES THEREFOR FOR HYDRAULIC I'RANSMISSIONS l Josef Hock, Friedrichshafen-Mame, and Friedrich F.

Schiippel and Ferdinand A. I. Baumann, Friedrichshafen, Germany, assignors to Zahnradfabrik Friedrichshafen, Friedrichshafen, Germany Application December '1, 1955, Serial No. 550,445 Claims priority, application Germany December 3, 1954 10 Claims. (Cl. 1374-468) This invention relates to pressure.v control systems especially for hydramatic transmissions, in which a gradual' increase in operating pressure is desired.

It has heretofore been customary to install a ow control nozzle in the pressure pipe line of hydramatic transmissions; such nozzles have a sharp edge on the vupstream side and are rounded on the downstream side. This eff fects a delay in reaching the full coupling-pressure. The arrangement, however, has the disadvantage that the cross-section of the pressure line leading the the coupling is narrowed down at the nozzle whereby disengagement of the coupling is also delayed.

Accordingly it is an object of the present invention to overcome this disadvantage and to provide a simple, inexpensive and rugged' mechanism for achieving such'purpose. Other objects and features of the invention w'll be apparent from the description to follow. v

The present invention contemplates a hydraulically controlled high pressure by-pass or reliefvalve assembly having a valvepiston and a control piston, the -latter exerting force through springs'against the valve piston to control its motion. The pressure chamber of the relief valve is connected with the pressure line and a discharge line. The spring resistance and the diameters of the valve piston and the control piston are of such proportions as to elect the desired delay of pressure iluid to the coupling by initially by-passing the iluid to the supply tank. Since the control piston is operated by fluid pressure through a flow delay device, the rate of motion lis controlled, thus controlling the valve piston.

In most forms of the invention, a one-way throttling device is installed in the connecting lline between the control pistonand the pressure line. This results in a delayed action of the control piston and thereby a gradual increase ofthe coupling pressure only when the valve is operated. When pressure on the valve is relievedithe de laying effect of the throttling device is neutralized, so

that the valve can return quickly to its starting position. Thus, the valve isuseful in cases where he changing of gears of several couplings in quick succession is needed. Further details of the invention will be understood from the following description in conjunction with theappended drawing in which: V

- Fig. 1 shows a relief valve with a centrally placed .feed line to the control piston;`

r' Fig. 2 shows a system of controlvfor several couplings with an oil pressure valve having quick relief action;

. i Fig 3 shows a partial section of an adjustable vstop vwhich may be used in the-'system of Fig. 5 to predeter- Amine the timingof 4the system; t

' Fig. 4 shows a relief valve with an auxillary chamber;

4of the control piston 42. Vof the arrow through line 46 into the chamber 44 of the 2,935,999; Patented May 10, n 19.6?

The oil llows in the direction valve housing 47. Thereby the spring-loaded piston 41 is pressed lout of rest position at the leftl end of the housing 47 until it reaches approximately the position shown; as a result the'discharge channel 48 has been partially opened. An oil pressure is built up corresponding to the pressure of the spring 49;-tbis pressure passes through the :line 43 via openings 50 and 51 into chamber? 45. ,In l0 consequence of this pressure a slide valve 5,2, equipped -with a ring-shaped throttling aperture 55 is pressed against la stop shoulder 53, and, in this position, closesjapbleed orifice 54. The oil enters through the throttling'aperture 55 between'the slide valve 52 and the pipe 43 into Vthe chamber 58 to the face lof the control piston 42, and presses the latter in a delayed movement asrfarras the stop shoulder 56. Simultaneously the highest coupling pressureV p2 is building up on the face of valve piston`4'1. An opening l57 serves for bleeding of the chamber'fand -for drawing off the leak-oil between the pistons 41 and 42.

' After the coupling has been disengaged, the oil which has been displaced by the retreatingpiston 42 moves the slide valve to the right and therebythe opening 54 is exposed so that oil can ow back freely into the oil-sump,

by-passing the throttling aperture 55. The pistons 41 and `42 return immediately totheir rest positions. V.'llherefore,

there is no delay in shiftingandthis valve can beused for -the shifting of several couplings in quick succession in conjunction with a distributor arrangement.

Fig. 2 shows a systemfor a relief valve withjquick Yrelief for shifting a plurality ofcouplings, e.g., rfour cou- Yplings. -The gear pump 63 sucks the oil from` the oil sump 59. vThe pressure oil flows through line .64`toth'e fface of the valve pistonv60. The valve piston 60 is thus shifted to compress spring'66 until the discharge port/,67 is opened and oil can flow back to the oil` sump 59 through line 68. Thevalve piston 60 is shifted until Vthe pressure exerted by spring `66 and the oil pressure in line 64 are balanced. A line 78 draws off the leak oil from the chamber between pistons 60 and 71, the controllpistom and lcarries it back to the sumn. f

Vsimusneouny with Huid loading of :valve pstbnlo,

pressure'oil flows through the connecting line 69 to a `chamber 77 in which a slide valve 70 has been'installed. The latter contains a throttling orifice 73.` The movable y' slide valve 70 is pressed to the left against va stop shoulder yin .the housing 65, and the pressure oil flows gradually through the throttlingforice 73 against the face of the Vcontrol piston 7l, ywhich'llatter is pressed to the Vleft it'meets Va stop element or -pin 61. Thus,the discharge port 67 is narroweddown and the oil pressure increases.

-Pin 61 may .be solenoid controlled to be withdrawn from :the path of piston 71 or to limit the travel of the piston,

so that the pressure valve in the pressure line can bead- .j-usted at will to either oftwo pressures. The pin `can be-operated simultaneously with one of the valves Slfto S4. If the the .pin is pushed forward, the piston 7'1 stops inthe intermediate position as shown in the drawingf The Y pressure which builds up in the pressureV line 79 isfan intermediate value governed by the pressure ofthe spring 66V for the pentinent position of the piston 71. The value can -be determined through adjustable positioning of pin Thus .the device can'be used 712. or 61, Fig. 2, the thrust of the control piston, and with ,-Fg..5 shows a cross section of an adjustable, thermo` v' Fig. 1 shows a valve with'a central line 43, vbetween a fchamber. 44 of the valve lpiston 41 and the chamber 451.

it, the pressure in the pressure line is limited to oneo'r to Ytwo pressures. However, a pin 161 (Fig. 3) movable in the direction of the thrust could also be utilized so as 71 to effect any choice of pressure in line 79. Y Through f the' ldelaying effect of the small-opening 73` in the slide to be disposable at any .desired point in the path of piston the thrott-ling port "and, as a result, a predetermined rate of ow of the oil 3 valve 70, the movement of the control piston 71 is delayed so that a certain time elapses until the discharge channel is narrowed down to its smallest value and the sgr'eatest pressure has been built up `in the pressure'line. The operating 'pressure in the couplings 'K1 to K., rises with corresponding slowness; these couplings can be connected according to choice with the pressure line 79, -by means oftvalvcs S1 to S4, located in control block? `When a valve S1-S4 is operated, the pressure line is rst yconnected with a bleed line 75 via a bleed valve 0, whence the relief valve 60 is relieved. The pistons 60 and 71 are instantaneously pressed back intotheir star-ting position by spring 66. The quick return of the control .piston 71 is possible because the slide valve 70 is pressed to the right by the returning oil and thus opens up the `bleed line 76. Y Y

yFig. 4 Vshows a relief valve with an ante-chamber. The relief valve consists of a valve .piston 80 and |the control .piston 81. The two pistons have different dia-metersl and are biased against each other through spring S2. The

fchamberv83 at the face ofpiston 80 is connected through fline 84 with chamber 85 which is sealed oiltight by auxiliary piston 86. Through auxiliary piston 85 and ,control piston 81 and ante-chamber 94 is formed, which -has a throttle orice 88 and which is closed against the remainder of the oil How system. It is possible to prevent impurities from getting into the throttle-orice, because the oil that is locked in the ante-chamber 94 cannot rnix with the transmission oil. The available thrust of the auxiliarypiston 86 must be greater than the thrust ofthe control piston 81.

In order to avoid the spraying of the oil, the discharge line 89 is connected by means of a line 91 directly with -`theoil sump 93; the valve may also .be surrounded by a housing which is connected with the oil Vsingle line.

vIn order to avoid the diminshing of the eteetive thrust of the piston 86 through escaping of oil romgthe antesump by a VVchamber 94, the chamber 127 between the pistons 80 and 81 is iilled with oil and is connected with the dis- `placement chamber 90 by means of a line 126. The

cham-ber`90 is connected wi-th the oil sump 93 by means Vofa bleed line 92.

`rFig. 5 shows a throttling arrangement with an adjust- -able throttling port 105.

` The throttling arrangement has been constructed as a centrally located connecting line I in the manner of line 43 of Fig. 1.

The method of operation of this valve is similar to that of the valve shown in Fig. 1 except for the operation llof the throttling arrangement. The hollow valve `stern 101 is screwed by means of a thread 1012 into the housing When the valve is -under pressure, the oil ows through the hollow stem 101, through the openings 104, Ito the throttling port 105, and then into -thechamber of the control piston 123. Through a threaded sleeve 106, 105 can be set to a certain dimension 4in'a-terial with a smaller coefficient of heat expansion than the valve stem 101; the housing for example is made of steel, the valve stem of brass. At an increasing temper- Y 'ature and consequently diminishing viscosity of the oil,

the valve stem 101 expands more than the housing 100; that is to say the throttling port 105 is vnarrowed down. As a result ow rate of the oil with a diminished viscosity hardly changes. In order to achieve a greater difference in heat expansion, the housing 100 can be made of Invar steel or a similar iron-nickel alloy.

Fig. 6 shows a further form of a thermostat'ic'throttle which'operates only in one direction of the flow; in the other direction it allows the oil to pass through freely. The throttle consists of a valve stem with the valve cone 111 and the guide cylinder 112. The valve stem runs in the duct 1'13. The duct 113 is mounted inithe pistons 122 and 123, which are equipped with packings 121; these pistons correspond to the valve piston 41 or the control piston 42, respectively, as shown in Fig. 4. lO11 the end of duct 113 there are openings 114 and '115. Both the cone 111 and the cylinder 112 are provided with flats 116 and 117; as a esultihollow spaces are formed through which the oil flows.V The throttling aperture 119 is adjusted through a threaded sleeve 118. ln order-to make this throttle valve thermostatically responsive, the valve stem 110 has been made of a material with a greater coeicient of heat expansion than the duct 113. The thermostatic eifect can also be effected or increased, as

Ythe case may be, by vusing a guide plate made of Bimetal, instead of the guideeylinder 112; the guide plate is screwed or riveted on to the valve stem 110 in such a manner that it willhave the same working results as the thermostatic arrangement described above, which uses different materials for the valve stem and the valve v housing.

When the valve is under pressure, the oil flows in the direction of the arrow through the throttle valve, and in Vdoing so, presses the valve stem 110 against the shoulder 120 of the duet 113. The aperture 119 between cone 111 and threaded sleeve 118 is thus narrowed down and functions as aV throttle. reduced, Ythe oil ows through the throttle valve in the When pressure on the valve is lit with undiminished speed and the valve is immediately relieved.

The invention is for hydraulically controlled by-pass or relief -valves having a valve piston and a control piston 'biased against the valve piston with a spring, and having a pressure chamber connected with a pressure line. The spring force and the diameters of the valve piston and the control piston are so proportioned that after a balance between the spring force and the oil pressure against the valve piston has been established, a force resulting 'from spring action and oil pressure acts upon the control piston. In `a line connecting the control piston with the pressures line, a ow delay device is inserted, which -regulates the movement of the control piston.

fHavingthus described our invention, we are aware that various changes may be made without departing from the spirit thereof and, accordingly, we do not seek to be limited to the precise illustration herein given except as set forth in the following claims.

We claim:

l. A delay action by-pass valve system for hydraulic transmissions, comprising a pressure line, a by-pass valve means communicating withsaid pressure line,'a discharge line communicating with said vvalve `means, said valve means being actuatable by pressure fluid from said pressure line to by-pass fluidfrom said'pressure line to said discharge line `so as t'o reduce the Vpressure to a predetermined value' in said pressure line,'and means for actuating said valve means to block passage of uid from-said -pressure line't`o said rdischarge line during the'course of a predetermined interval of time; whereby` fluid'pressure is transmitted at a 'selectively increasing degree'from a minimumlto a: maximum 'valuesaid .vlve meansicompi'ising 'a valve piston and a` control piston, including-fa spring element intermediate said .pistonsjfa respective chamber for each piston and in which said'fpistonsfare movable, said pressurel line vcommunicating@withy the chamber of said valve piston atall times, said discharge line communicating with said valvel piston chamber and disposed to be cut oli from said chamber by movement of said valve piston, means communicating pressureoil from said pressure line tothe chamber of said control piston through a restricting iiow throttle, means' whereby said control piston can overpower saidV valve piston'to shut off tluid flow from the valve piston'chamber 4through said discharge line within'a' predetermined time effected byow through said throttle, wherein said means cmmunicating-pressure' oil from 'said pressure line to the chamber of said control piston'cornpris'e's a tube passing co'nc'entri'callyl through v said pistons.: v

2. In a device as set forth in claim l, said throttle being effected by an additional valve -pistonsurroundng saidl tube and/'having a central port" 'spaced' therefrom t eiect a how-restricting annular oriiice,a` chamber'surrounding vsaid additional piston having ableed port, wherein said additional valve'piston may move to cover or uncover said bleed portl to 'bleedI said chamber, and being moved'to block said port byl pressure ow through 'said'tube from saidfvalve piston'charnberand.,l being reversely movedto'nncoverl said-portupon said latter valve being actuated in the reverse direction by'rn'oyel lrnent of said control'p'iston subsequent to4 release f pressure'in` saidv pressure vline'by fluid trapped'intermediate l said control piston'vandsaid additional valvefpiston'.

" f3; A delay actionby-pass valve system for "hydraulic transmissions, comprising a pressure line, a bjr-pass valve means communicating with said pressure line, a discharge line communicating 'with said valve means,'s`aid valve means being actuatable by pressure'luid from said pressure line to by-pass Huid fromsaid pressure line to said `discharge :line so as to reduce the pressure to a predetermined value in said pressure line, and means for actuating said valve means to block passage of fluid4 from said pressure line to said discharge line during the course'of a predetermined interval of time; whereby iiuid` pressure is transmitted at a seletivelyrincreasing degree from a minimum to amaximum valuepsaid valve means comprsing a valve piston and ancontrolpiston and aspring intermediate said pistonswwhereby force exerted on said control pistons may be transmitted through said spring to move said valve piston, a chamber for each of said pistons, said pressure line being connected to said valve piston chamber and said discharge line being connected to said valve piston chamber whereby movement of said valve piston may serve to block ow of pressure uid from said pressure line to said discharge line and means for communicating said control piston chamber with said pressure line for eiiecting movement of said control piston, said means including a restricted ow orifice so as to delay motion of said control piston for a pre-determined degree of time, said restricting flow orifice comprising elements of difering heat coeicients, to reduce or enlarge the ow rate through said orifice in accordance with the temperature of the pressure uid in said pressure line so as to maintain a substantially uniform rate of iiow.

4. A delay action by-pass valve system for hydraulic transmissions, comprising a pressure line, a by-pass valve means communicating with said pressure line, a discharge line communicating with said valve means, said valfve means being actuable by pressure fluid from said pressure line to by-pass iluid from said pressure line to said discharge line so as to reduce the pressure to a pre-determined -value in said pressure line, and means for actuating said valve means to block passage of uid from said pressure line to said discharge line during the course of a pre-determined interval of time, whereby uid pressure is transmitted at a selectively increasing degree from a s6 to a maximurnvalue, said valve means comprising a valve piston and a` control pistonfincludingra spring element intermediate said pistons, a respective chamber' for each piston and in which'said pistons. are movable,said pressure line communicating with the chamber of said .valve piston at all-,timesgsaid discharge line communicating with said valve piston chamber4 and dis posed tobe cut-olf from said chamber by movementlof said valve piston, .means communicating pressure oil from said pressure line to the chamber of said -control `piston through a restricting iiow throttle, means whereby said control piston can overpower saidvalve piston to shut olf ow uid from the valve, a piston chamber throughsaid discharge line within a pre-determined time eiectedaiby iiow through said throttle, wherein said meansicommuni cating from said pressure line to the chamberofisaid control piston comprises a tube passing concentrically through said pistons, at least one of said-pistonsxbeing slidable on said tube. v I a E :f

5. A delay action by-pass valve system for= hydraulic transmissions, whereby uid pressure is transmitted to a transmission at a selectively increasing degree from a minimum to a maximum value, comprising'a pressure line, a by-pass valve means communicating with said pressure line, a discharge linet:ommunicatingvvith said valve means, said valve means being actuable by pressure uid from said pressure line tovby-pas`s fluid from said. pre'sf sure zline to said discharge line-.so as 'to reduce the pressure to a predetermined value in said pressure linegfsaid valve means comprising a-valve piston zdirectlyexposed 'topre'ssure in said pressure line, Va control piston,fa thrust ele"- mentA intermediate said pistons,y means Wherebyfcrce exertedon saidv control pistor'rmay beV transmitted through said thrust element to said .valve piston to overcome the pressure thereon ,so as to :block flow of pressure' uid from said pressure line to said discharge line, and-means for communicatingsaidcontrol piston chamber=with `said pressure line for effecting movementof saidA control :piston, saidmeans including a restricted'oworicerto delay motion lof said control piston thru a pre-'determined degree of time, said restricting ow orice comprising elements of diiering heat coeiiicients,v to reduce or enlarge the flow rate through said orifice inaccordance Awiththe temperature fof the pressure uid in said pressure line? so as to maintain a substantially uniform ,rate of now thru said orifice. -6.-A,d'e1ay action by-pass valvefsystern forfafhydraulic transmission, comprising a pressure line, a 1 by-pass :valve means communicating with said pressure line, a discharge line communicating with said valve means, said valve means being actuable by pressure uid from said pressure line to by-pass Huid from said pressure line to said discharge line so as to initially reduce the pressure to a predetermined value in said pressure line, and means for actuating said valve means to block passage of fluid from said pressure line to said discharge line during the course of a pre-determined interval of time, whereby uid pressure is transmitted at a selectively increasing degree from a minimum to a maximum value, said valve means comprising a valve piston and a control piston and a spring intermediate said pistons whereby force exerted on said control pistons may be transmitted through said spring to move said valve piston, a chamber for each of said pistons, said pressure line being connected to said valve piston chamber and said discharge line being connected to said valve piston chamber whereby movement of said valve piston may serve to block ow of pressure iluid from said pressure line to said discharge line; means for communicating said control piston chamber with said pressure line for effecting movement of said control pis` ton, said means including a restricted iiow oriiice to delay motion of said control piston for a predetermined degree of time, said restricting flow orifice comprising elements of diering heat coeicients to reduce or enlarge. the iow rate through said oriiice in accordance with the temperature of the pressure uid in said pressure line so as to maintain a substantially 'uniform rateY of -ovv` thru said orifice. 1

7. A delay' action by-pass valveY system forl hydraulic transmission, comprising a pressure line, a by-pass Ivalve means communicating with said pressure line, a discharge line communicating with said valve means, said valve 'means being actuable byrpre'ssure fluid from said pressure line to by-pass iiuid from said pressure line to said discharge line so las 'to reduce the pressure to a pre-determined value in said pressure'line, and means for actuating said valve means to. block passage of fluid from said pressure line to said discharge line during the course of a pre-determined interval of time, whereby uid pressure is transmitted at a, selectively increasing degree from a minimum to a'maximum value, said valve means comprising avalve piston' and a control piston and a thrust element intermediate said pistons whereby pressure exerted on said control piston may be transmitted through said thrust element to move said valve piston,'a chamber for each of said pistons, said pressure line being connected to said valve piston chamber and said discharge line being connected to said valve piston chamber whereby movement of said valve piston may'serve to block flow ofpressure uid from said pressure line to said discharge line, and meansv for communicating said; control piston chamberwith said pressureline for effecting movement of said control piston, said means including a restricted ow orifice sovas, to delay motion of said control piston for apre-determined degree of time, said means for communicating said control piston chamber with said pressure line comprising a nid passage means concentric with said valve piston and said control piston wherein said duid-passage means comprises a vtube passing co-axially through said pistons, at least `oneof said pistons being slidable on said tube.

8. A delay action bypass valve system for hydraulic transmission, 'comprising a pressure line, a by-passfvalve means communicating with said pressure line, a discharge line communicatingl with saidl valve means, said valve -means being actuatable by pressure uid from said pressure line to. by-pass fluid from said pressure lineV to said discharge line so as` to'reduce the pressure to a pre-determined valuein said pressure line, and meansV for actuating said valve means to block passage of iluid from said pressure line to said discharge line during the course of a pre-determined interval'of time, Vwhereby fluid pressure is transmitted at a selectivelyv increasing degree from a to a maximum value, said valve means compris- 'mg a valve piston and a control piston andA a thrust element intermediate said pistons whereby pressure exerted on said control piston may be transmitted through said thrust element to move said valve piston, a chamber for each of said pistons, said pressure line being connected to said valve piston chamber and said discharge line being connected to said valve piston chamber whereby movement of said valve piston may serve to block flow of pressure'uid from said pressure line to said discharge line, and means for communicating said control piston chamber with said pressure line for effecting movement of said control piston, said means including a restricted ow orice so as to delay motion of said control piston for a predetermined degree of time, said means for communicating said control piston chamber with said pressure line comprising a fluid passage means concentric with said valve piston and said control piston wherein said Huid passage means comprises a tube passing co-axially through said pistons, said tube having an orifice element and an elongated member withn said tube comprised of a material having a higher coeicient of heat expansion than the material of said orice element and having a head disposed adjacent said orifice element, whereby contraction and expansion of said elongated element responsive to temperature of fluid contiguous thereto effects variable spacing for uid `How between said head and said orifice element.

9. In a device as set forth in claim 7, both of said pistons being slidably disposed on said coaxial tube.

10. In a device as set forth in claim 8, said elongated member being secured to and carn'ed by said tube adjacent one end thereof.

References Cited in the tile of this patent UNITED STATES PATENTS 514,394 Henderson Feb. 6, 1894 618,903 Prince Feb. 7, 1899 2,002,451 Gray May 2l. 1935 2,064,343 Finley Dec. 15, 1936 2,109,958 Finley Mar. l, 1938 2,283,311 Bevins May 19, 1942 2,610,300 Walton Sept. 9, 1952 2,649,688 Slomer Aug. 25, 1953 2,720,294 Hindmarch Oct. 11, 1955 2,721,640 DeFeo Oct. 25, 1955 Patent No@ 2,935,999

May 10, 1960 Josef Hook et al.,

It is hereby certified that error a ent requiring correction and that the sa corrected below.

ppears n the above numbered patid Letters Patent eshould read as Column 1, linee 17 and 2OY for i"hydramal-tic", each occurrence, Feed m Hydra-Matic -e-o Signed and sealed this 2nd day of May 1961.,

(SEAL) Attest:

ERNEST Wn SWIDER DAVID L LADD Attesting Officer Commissioner of Patents 

